Minimizing hydrate formation

Judy Maksoud
International Editor
Offshore

The best way to deal with hydrates is to keep them from forming. Scott Budd, a chemical engineer with Nalco, told participants at the Offshore West Africa conference there are several options for preventing hydrate formation. Budd listed heat management, pressure management, and chemical inhibition as alternatives.

Budd focused on chemical inhibitors, subdividing them into thermodynamic inhibitors and low-dose hydrate inhibitors (LDHI).

Budd presented test results from a sample of Nigerian crude as a case study and showed how testing using a rocking cell that simulates fluid movement in a pipeline is used for evaluating hydrate inhibitors.

The test evaluated methanol, kinetic hydrate inhibitor (KHI), and anti-agglomerates (AA). All three are viable, according to Budd, but not equally so.

According to the test results, methanol, though effective, is costly and must be used in large volume, which creates logistic issues. KHI works at 3.5% concentration. And a combination of 20% methanol and 2% KHI also resolves the hydrate formation problem.

The most effective solution, Budd said, is AA, which works efficiently at 1% with a 50% water cut.

"AA," said Budd, "have nearly unlimited subcooling," which broadens the scope of their application. AA work well for continuous use, start-up, and shutdown, he said.

03/21/05